Recent NH3-SCR Mechanism Research over Cu/SAPO-34 Catalyst

The preliminary mechanism research of NH 3 -SCR and NH 3 oxidation over Cu/SAPO-34 catalyst is explored. The XRD, SEM, in situ EPR, NH 3 -SCR, NH 3 oxidation test, DRIFTs, and the kinetic tests were performed for the bulk characterization, catalytic activity measurement, and the mechanism estimation. The NH 3 -SCR result showed that Cu/SAPO-34 revealed excellent activity during 120–600 °C, while the NH 3 oxidation appeared above 300 °C and caused the decline of NO conversion. The order of various reactants (NO, NH 3, and O 2 for NH 3 -SCR and NH 3, O 2, for NH 3 oxidation) was estimated by the kinetic tests to explain their behaviors during the NH 3 -SCR process. The NH 3 -SCR presents strong dependence on adsorbed NH 3 species on Cu/SAPO-34, but the NH 3 oxidation does not. Furthermore, the EPR experiment proved that the isolated Cu 2+ species are the active sites and the ammonia nitrites species are the intermediate for NH 3 -SCR over Cu/SAPO-34 catalysts. The different behavior of adsorbed NH 3 species in NH 3 -SCR and NH 3 oxidation was studied through DRIFTs to explain the competition between the two reactions for NH 3 consumption at high temperature. Meanwhile, combining the results of previous research, the primary reaction mechanism over Cu/SAPO-34 during the NH 3 -SCR process was conducted.